In 2009, they had more than 50 members. One wave election later, half their members were gone.

And now, in a Congress marked by its uncompromising partisanship, just 15 of the so-called “Blue Dog” Democrats remain.

The Blue Dog coalition, mostly Democrats from Republican-leaning or swing districts, were a one-time moderating force within the House Democratic Caucus, and their influence was felt on some of the most divisive issues facing Congress. In the debate over Obamacare, it was the Blue Dogs who convinced fellow Democrats to back away from liberal demands for a single-payer, government-run health care system, which had stalled negotiations.

But as the Blue Dogs' numbers dwindle, so has its influence. They are outnumbered now by deeply ideological lawmakers elected from homogenous, custom-gerrymandered districts and out-gunned by outside interest groups whose growing influence on Capitol Hill strikes fear into the hearts of any lawmakers tempted to seek middle ground.

The Blue Dogs' membership is still in decline. Rep. Jim Matheson, D-Utah, announced that he will retire after his current term. Rep. Mike Michaud, D-Maine, is leaving to run for governor. And other Blue Dogs face competitive re-election bids in 2014, meaning the coalition could shrink even further.

Then again, maybe not.

“The rumors of the demise of the coalition are somewhat exaggerated,” said Paul Gage, chief of staff to Blue Dog Rep. Kurt Schrader, D-Ore. “The path to a Democratic majority is through purple and red districts that Blue Dogs know how to win.”

It’s unlikely Democrats will reclaim the House majority in 2014, however — so, for the Blue Dogs, a comeback is a waiting game, a gradual slog of rebuilding by taking back swing districts from moderate Republicans.

Until the House swings back to Democratic control, the Blue Dogs are striving to remain relevant even though they're no longer at the forefront of the political conversation.

“They’re still a very tight-knit group,” Gage said. “They still meet weekly, if not more than weekly,” including in joint meetings with the moderate “Tuesday Group” of House Republicans.

The Blue Dogs’ plight speaks to the greater electoral obstacles faced by Democrats as they try to gain seats in the House and, ultimately, scheme to win back a majority. After Democrats suffered a historic loss during the Republican wave in 2010, election districts were redrawn to favor Republicans, helping keep the GOP in charge of the House.

The dynamic has also contributed to the hyper-partisanship that has characterized this Congress, driven by lawmakers who have had little appetite to forge compromise — perhaps best embodied in the legislative gridlock that led to a 16-day government shutdown last year over Republican qualms with Obamacare.

Democrats hoped for a spurt of political momentum after the government shutdown, which voters blamed on Republicans, but that issue has since been obscured by the rocky rollout of the president’s health care law.

However, the government shutdown has bred cautious optimism among Democrats that pro-business groups, such as the Chamber of Commerce, could choose to support moderate Democratic candidates over staunchly conservative Republican opponents. Indeed, Democratic Congressional Campaign Committee Chairman Steve Israel, D-N.Y., has made the case to business interests ahead of this year's elections that their money would be better spent on moderate Democrats than in trying to fend off Tea Party primary challengers.

Such an alliance would not be without precedent: The Chamber in 2012 supported two Blue Dog Democrats: Matheson and Rep. John Barrow of Georgia.

But to win support from voters and outside groups, Democrats caution, moderate Democrats of the Blue Dog ilk must distinguish themselves from Republicans.

“They’ve been focused on debt and the deficit, but I do think they need to expand that a bit to middle-class pocketbook issues” like education and jobs, said Doug Thornell, a former Democratic Congressional Campaign Committee spokesman now with SKDKnickerbocker. “Sometimes I feel like they’re competing on the same plane as Republicans.”

Thornell added, “When someone appears to be a Republican-lite candidate, people tend to go for the Republican.”